A study at Duke University found:
“Inhalation of O(3) is associated with impaired antibacterial host defense, in part related to disruption of epithelial barrier and effective phagocytosis of pathogens.”
The EPA released a statement about air cleaners emitting ozone:
Manufacturers and vendors of ozone devices often use misleading terms to describe ozone. Terms such as “energized oxygen” or “pure air” suggest that ozone is a healthy kind of oxygen. Ozone is a toxic gas with vastly different chemical and toxicological properties from oxygen. Several federal agencies have established health standards or recommendations to limit human exposure to ozone.
The EPA further commented that:
Ozone generators sold as air cleaners and marketed as in-duct or portable units use UV light or corona discharge to produce ozone, which is dispersed by a fan into occupied spaces.
Some manufacturers and vendors of ozone generators suggest that ozone reacts with both chemical and biological pollutants and transforms them into harmless substances. They also often make statements and distribute materials that lead the public to believe that these devices are always safe and effective in controlling indoor air pollutants. However, ozone is an irritant gas that reacts with lung tissue and can cause asthma attacks; coughing; chest discomfort; irritation of the nose, throat, and trachea; and other adverse health effects. As ozone reacts with chemical pollutants, it can produce harmful by-products.
Other air “cleaners” create toxic compounds such as hydrogen peroxide, hydroxyls, and superoxide ions. Indeed one company states that these compounds are “friendly cleaners”. However, these compounds create oxidative damage which uses up your antioxidant defenses, leaving the body more susceptible to other insults.
In other words, it is probably a good idea to avoid products that produce and emit ozone or other oxidizing compounds. This can also include air cleaners that ionize the air (which can create ozone).
If you are looking for a high quality air cleaner, consider one from IQair for hyper-HEPA filtration, and another called Airfree, to help passively kill microbes and mold spores without releasing any toxic chemicals into the air.